The present invention relates to a magnetic head used in a magnetic recording device and more particularly to the structure of a magnetoresistive head used as a read head.
Recently, techniques for improving the surface recording density have been developed in order to attain high performance of magnetic recording devices. Improving the surface recording density needs to attain a high track density and a high linear recording density. In addition, it is essential to narrow the track width and read gap of read and write heads as magnetic heads.
The schematic structure of a conventional read head is shown in FIGS. 15 and 16. This read head includes a magnetoresistive element 1 (hereinafter referred to as “GMR element”) using GMR effect as a read element, electrode layers 3 disposed at both the ends of the element 1 to supply electric power, and magnetic domain control layers 2 disposed at both ends of the element 1 to control magnetic domains of the read element. In addition, the read head includes upper and lower magnetic shield layers 5, 6 having soft magnetic characteristics which are disposed above and below the above-noted element and layers through insulating layers, respectively.
An effective track width of the read head is basically determined by a geometric track width of a GMR element which is defined as the distance between a pair of electrodes formed on the magnetic domain control layers. However, it is also influenced by the strength of magnetic domain control and the spacing between the magnetic shield layers. The electrodes and magnetic domain control layers are formed at the end portions in the track width direction of the GMR element. Therefore, the film thicknesses of the end portions are larger than that of the GMR element. Consequently, the spacing between the magnetic shield layers at the end portions becomes greater than at the central part in the track width direction. In particular, as the track width is made narrower, the geometric track width of the GMR element becomes narrower, so that the increased spacing between the magnetic shield layers becomes more influential, leading to a substantial increased track width. This phenomenon is called side reading at end portions of the read element. The phenomenon occurs in a distance range approximately equal to the spacing between the upper and lower magnetic shields in the read element height direction from an air bearing surface of the magnetic head. This causes deterioration of resolution at end portions of the geometric track width and cross talk with an adjacent track. Thus, the phenomenon in question is a serious problem in narrowing the track width.
As methods for avoiding this problem, various techniques are disclosed, for example, in Japanese Patent Laid-open Nos. 6-60326, 11-25431 and 2004-206842. The techniques include a technique of making electrodes and magnetic domain control layers as thin as possible and a technique of using thin electrodes to stepwise prevent an increase of the shield spacing.